New meson configuration in the bag model (I). First order energy spectrum of qqg states

Perturbative QCD in the bag is applied to unconventional configuration of quarks and gluons. The meson spectrum is computed to second order in the strong coupling. Exotic states with J^PC = 1^?+, 0^+?, 0^?? are found in the energy range 1.57 ? E ? 1.93 GeV.     

New physics effects from B meson decays

In this talk, we point out some of the present and future possible signatures of physics beyond the Standard Model from B-meson decays, taking R-parity conserving and violating supersymmetry as illustrative examples. An expanded version is available on hep-ph archive.     

Nuclear deformations in the pairing-plus-quadrupole model (II). Discussion of validity of the model

This paper attempts to choose the parameters of the pairing-plus-quadrupole model as realistically as possible. A correction is introduced to take into account the different numbers of neutrons and protons. An expression is given for the deformation energy of a nucleus with an arbitrary two-body interaction. Then the pairing-plus-quadrupole matrix elements are compared with those of more realistic interactions, and it is decided to keep only matrix elements between states of two adjacent oscillator shells. An argument is given to determine a priori the strength of the quadrupole force, and various corrections to this are discussed. No similar argument is found for the pairing force. Residual effects of the remaining oscillator shells are included in an approximate fashion. Comparison with previous work along these lines is presented.     

A prescription for removing centre-of-mass effects from the bag model

We assume that the state of the MIT bag model describes a hadron which itself is confined to a spherical region of certain size. By demanding that the low energy levels of the quark system and that of the confined hadron coincide we determine selfconsistently all relevant parameters and calculate the Roper resonance mass.     

Instanton effects in meson spectroscopy

In this contribution, the results on the spectra and semileptonic decays of light and heavy mesons in a relativistic constituent quark model incorporating a confinement potential as well as a residual interaction induced by instantons are reported.     

Masking patterns in the bullfrog (Rana catesbeiana). II: Physiological effects

Responses of individual eighth-nerve fibers in the bullfrog (Rana catesbeiana) were measured to tone bursts at best frequency against a background of continuous, broadband masking noise. These data were used to calculate critical masking ratios to describe the fibers' responses to tones embedded in noise. In the frequency response range of the amphibian papilla (100-1000 Hz), critical ratios increase with tone frequency. Critical ratios of basilar papilla fibers (1000-2000 Hz) are generally higher than those of amphibian papilla fibers. Critical ratios are also significantly related to fiber threshold such that fibers with high thresholds, regardless of their best frequencies, have higher critical ratios and are thus less selective to signals embedded in noise. Critical ratios based on neural responses show a somewhat different frequency-dependent trend than do critical ratios based on psychophysical data presented previously for this species [A. M. Simmons, J. Acoust. Soc. Am. 83, 1087-1092 (1988a)]. In addition, these neural critical ratios do not appear to be level independent, as are psychophysical critical ratios. The data suggest that frequency selectivity of hearing in the bullfrog as measured behaviorally is probably not mediated solely by spectral filtering in the auditory periphery.     

Mixing of meson isosinglets in SU(5) and an extension to SU(N)

The mixing angles of meson isosinglets belonging to the 24-dimensional and singlet representations of SU(5) are calculated under specific assumptions in the non-relativistic quark model. The procedure to extend the scheme to SU(N) has been outlined. The results have been compared with other earlier estimates.     

Vacuum energy in the bag model

The vacuum energy of the Yang-Mills field is examined for the conditions of the bag model. The dominance of high-frequency effects results in a vacuum energy that decomposes naturally into a volume energy, a surface energy, and higher shape energies. These quantities are identified with the parameters of the bag model. The imposition of confining boundary conditions for all frequencies is shown to be inconsistent since this would result in the bag constant and certain of the shape tensions being infinite. The manner in which the boundary conditions should be relaxed at high frequency is discussed. The most naive procedure for relaxing the boundary conditions, which is to apply confining conditions only on modes of frequency less than some cutoff frequency, results in a negative bag constant and surface tension and would render the vacuum unstable against the spontaneous breaking of Poincaré invariance. Consideration of the manner by which the interacting electromagnetic field avoids a similar instability suggests that a more realistic way to relax the boundary conditions on the bag surface is to endow the vacuum exterior to the bag with a frequency-dependent dielectric constant and magnetic permeability. In this picture the stability of the vacuum is restored, the surface tension is finite and positive, and the bag constant is zero at least to lowest order in the coupling. It is pointed out that the fermion contributions to the bag constant and the surface tension may relate to the spontaneous breaking of chiral invariance. The aim throughout is to examine the bag model, as it relates to vacuum energy, strictly in its own terms with an emphasis on questions of principle.All too often is heard the alibi that since the theory itself is only approximate, the mathematics need be no better. In truth the opposite follows. Granted that the model represents but a part of nature, we are to find what such an ideal picture implies, a result strictly derived serves to test the model; a false result proves nothing but the failure of the theorist. To call an error by a sweeter name does not correct it. The oversimplification or extension afforded by the model is not error: the model, if well made, shows at least how the universe might behave, but logical errors bring us no closer to the reality of any universe. (Truesdell and Toupin 1960).     

Vacuum condensates in the bag model

The consequences of having quark and gluon condensates inside a MIT bag are investigated. We show that one naturally expects a state dependent bag constant and a colour-magnetic interaction term ～R². This gives the possibility of having a small strong coupling constant α_s inside the bag.     

Mean-field expansion and meson effects in chiral condensate of analytically regularized Nambu-Jona-Lasinio model

Scalar meson contributions in chiral quark condensate are calculated in the analytically regularized Nambu-Jona-Lasinio model using the framework of mean-field expansion in bilocal-source formalism. The sigma-meson contribution for physical values of the parameters is found to be small. Pion contribution is found to be significant and should be taken into account for the choice of the parameter values.     

Exclusive semileptonicB decays in the bag model

Using a recoil corrected version of the MIT bag model, we compute the relevant form factors and decay rates for the exclusive semileptonic decays \(B \to De\bar v_e and B \to D*e\bar v_e \) . Our results are similar to other quark model calculations, but we find that theD ^* mode is suppressed due to the influence of the spectator quark. TheD ^*′ s produced are almost unpolarized in this model.     

Pion-nucleon scattering in the Brown-Rho bag model

Pion-nucleus scattering in the (3,3) resonance region is described using a version of the Brown-Rho bag model. Terms involving iterations of the crossed Born graphs, as well as excitation of the three-quark delta, both give significant contributions to the scattering amplitude.     

Proton polarizability in the MIT bag model

The polarizability of the proton is calculated in a simplified MIT bag model and compared with an analysis of Compton scattering. Qualitative agreement is obtained for the sum of the electric and magnetic polarizabilities, which is found to be within 30% of the experiment.